(i) Technical Field
The present invention relates to focal plane shutters and optical device.
(ii) Related Art
A focal plane shutter includes: an electromagnet; and a drive lever holding an iron piece, the magnetic attraction force being generated between the iron piece and the electromagnet. The drive lever drives blades. The drive lever is biased by a biasing member such that the iron piece is moved away from the electromagnet. The energization of the electromagnet is stopped in a state where the iron piece is adsorbed to the electromagnet, thereby moving the drive lever in accordance with the biasing force of the biasing member such that the iron piece is moved away from the electromagnet. The drive lever drives the blades by use of the magnetic attraction force of the electromagnet and the biasing force of the biasing member.
When the reciprocation of the drive lever is repeated for a short period, the posture of the iron piece might not be maintained constant. The variation in the posture of the iron piece occurs, whereby the variation in the posture of the iron piece also occurs when the iron piece abuts the electromagnet. This might make the variation in the timing when the iron piece is moved away from the electromagnet after the energization of the electromagnet is stopped.